Tashkent, Uzbekistan (UzDaily.com) -- The preliminary results of the third stage of trials of the vaccine against COVID-19 of the British-Swedish company AstraZeneca, announced on 23 November, became the subject of heated discussion by experts regarding the effectiveness of the drug.

Tests on over 20 thousand volunteers from the UK and Brazil showed an average efficiency of 70%. However, when two equally large doses of the vaccine were administered each month, the level of protection dropped to 62%. It increased to 90% when the volunteers first received a small and then an increased dose of the drug.

Experts point out that the different immune responses of the body with the introduction of large and small doses raises more questions about the reliability of the test results and the effectiveness of the vaccine. In this context, the following factors stand out.

First, scientists’ doubts about the safety of the vaccine are reinforced by the fact that the trial participants, who originally received the half dose, were 55 years old or younger. If the half dose has not been tested in older people, it will be difficult to get a vaccine approved for emergency use by country regulators.

Second, the confusion is exacerbated by the fact that AstraZeneca has pooled results from two different clinical trials conducted in the UK and Brazil. This is contrary to the usual practice of providing test results for medicines and vaccines.

Against this background, the developers have promised to start a new large-scale study. It is reportedly aimed solely at clarifying whether half doses are actually more effective than two standard doses.

WHO expects to complete an evaluation of the AstraZeneca vaccine by early next year.

Overall, despite these ambiguities, experts from around the world still agree that the vaccine from AstraZeneca is potentially the most affordable in the world. Among the advantages of the drug are: 1) no need to store it at very low temperatures - it can be kept in the refrigerator for 6 months; 2) low price (US$3-4 per dose); 3) the company’s plans to produce a large number of doses in 2021 - up to 3 billion.